The wall had stood for over six hundred years.

It had suffered the predations of the elements, enduring wind, rain and dust storms with a stoic nobility. The elements had smoothed its once sharp lines and softened its majesty, but it still towered over the landscape offering a tremendous view to all who walked upon its spine.

It was the last defence. A twenty-metre-thick curtain wall of stone that wrapped itself around the citadel at the heart of a fortress layered with many such walls. Within their protective embrace, fourteen of the Undying Emperors had ruled these lands with the utter certitude of their divinity and their inviolability.

The wall had fallen within twenty minutes of the first attack.

‘Keep going!’ yelled Karsis. ‘Don’t stop, don’t stop!’

The wind whipped at her as they bounced along, driving grit and stone into the unprotected parts of her face. Sharp fragments drew blood.

She ignored them all, her focus was entirely on the dark shape rapidly materialising out of the gloom in front of them.

They could make it. They had to make it.

To her right there was a ground burst, and she ducked involuntarily as a thousand razor sharp shards flew through the air. Most lacerated the sides of Old Night, but the doughty tank ignored them. Her thick skin would be covered with the poisonous barbs but that was the least of their concerns.

‘More speed!’ she yelled into the vox. But their pace did not increase.

Could Daylor hear her?

She was already half crouched in the commander’s cupola to avoid the ground bursts, so it was an easy matter to drop fully into the depths of the tank. 

‘Daylor,’ she screamed. ‘Did you hear me? More speed!’

The inside of the Leman Russ was infernally hot as always and the cacophony of battle was amplified a thousand times in here. She couldn’t even hear the sound of her own voice.

But nonetheless she saw Daylor’s left hand rise up, his fist clenched, and thumb extended upwards. Without turning from his viewport, the driver then tapped his hand on the vox unit at his ear. His right metal arm was clamped onto Old Night’s steering controls as if they were a part of him. Which in his case was almost true.

Besides her the burly sweating form of Jos slammed another shell into the breech and locked it in place.

‘Ready!’ the loader yelled, his voice somehow loud enough to rise above the din.

Karsis couldn’t see Eman on the other side of the breech, but his voice was as infuriatingly calm on the vox net as ever. She automatically pressed her hands over her ears and opened her mouth as she heard him speak.

‘Fire.’

Old Night rocked as the battle cannon roared again, hurling its payload into the storm. She had no idea what Eman was firing at, but she trusted him entirely. Besides, they were hardly short of targets.

She stood up in the cupola again, risking exposing her head to a lucky shot from outside. Most commanders would be buttoned up in a mess like this, but Karsis needed to see what was happening around them. Being buttoned up gave her tunnel vision and she inevitably found her gaze drawn to whatever the cannon was pointing at.

That would not be a problem here of course, since Old Night’s main gun was pointed squarely to their rear, blasting at whatever was pursuing them. It had been aiming that way ever since she had ordered the crew to turn tail and run. 

Her head came out into the open and her eyes blinked behind the goggles in surprise. The dark shapes ahead had materialised a lot closer than she was expecting. Daylor had heard her after all.

‘Brace, brace, brace!’ she screamed into the vox, and grabbed the lip of Old Night’s cupola.

The venerable tank smashed into the ruins of the fallen curtain wall and ground over them turning ancient stone into dust under its weight.

They had made it. They were inside.

---

The swarm had arrived over a week ago, but the signs of their coming were visible long before then, at least to those who had the eyes to see.

The approach of the hive fleet enveloped everything before it. It first arrived on a single vector, questing and writhing looking for a host body to infect. A quieter system might have been fortunate enough to be deemed too biologically insignificant to warrant anything more than the deployment of a single hive ship. But the over-populated worlds of Medusa had no such luck, and almost immediately after first contact the xenos hive mind directed a significant portion of its strength to absorb these worlds into its biomass.

As the living ships gathered at the edges of the system, their density began to block out the stars in that corner of the night sky. To anyone who looked up it was as if a dark hole had appeared within the void itself. A hole that began to spread.  

By now High Command was alerted to the presence of the xenos and the war machine began to mobilise. Vox stations began to blurt a repeated message to all who could hear them: This was but a small tendril that Medusa had both the might and the ammunition stores enough to withstand. Battlefleet Agriana was dispatched to stamp out this insidious foe before it could claim a foothold on a single world.

The strategos of the Imperium noted that the hive fleet was projecting a psychic bow wave before it as moved through the void, perhaps as a result of the concentration of so many potent minds forming a greater gestalt force. As the power of the alien mind washed over Medusa it wreaked terrible havoc on some of those it touched.

Gifted astropaths, blessed with the warp-sight, found their third eyes were either blinded or corrupted by visions of something utterly alien that had forced their way inside their heads. Many did not live long enough to scream, put down by the waiting bolters of the Astartes watching over them. They were the fortunate ones.

In the cities and villages across the world those who perhaps unknowingly carried a latent psyker gene found themselves utterly unprotected to the intrusion of the xenos will into their minds. Writhing in agony and clawing at their own eyes, many were driven insane, attempting to scream alien cries that no human mouth could articulate.

The touch of this psychic shadow began to interfere with long distance communication with outside systems. Those few astropaths who did survive found that less and less of their calls for help were being answered. The defending forces were forced to rely on simpler vox-traffic to communicate. But the vast distances between the planets and the fleets that guarded them meant that hours could pass before a message was received, and often by the time a reply was sent there were no living forces left to receive them.

When Battlefleet Agriana finally made contact with the hive, only rare and confused messages made it back to the waiting ears on the planets. But in time, even those stopped and only a brooding silence answered the repeated vox-hails from the worlds.

By now the dark hole in the sky had spread wider, and at its centre it began to emit a sickly hue of white and purple. A stain of inhuman flesh radiating from the trillions of bodies growing within it that grew stronger by the day.

As the swarming mass neared it became visible to the naked eye. A shifting cloud of living vessels approaching that sprouted off shoots like sticky claws reaching out to grasp the worlds.

Then came the rain. First there were a few, then many then an unstoppable horde of foreign bodies began to streak across the sky. Anti-air guns spun up and obliterated the first few hundreds, but still they came. The air was soon choked with them and wherever each of these spores struck the ground, the gunfire lessened.